/**
 * This jQuery plugin displays pagination links inside the selected elements.
 *
 * @author Gabriel Birke (birke *at* d-scribe *dot* de)
 * @version 1.2
 * @param {int} maxentries Number of entries to paginate
 * @param {Object} opts Several options (see README for documentation)
 * @return {Object} jQuery Object
 */
jQuery.fn.pagination = function(maxentries, opts) {
  opts = jQuery.extend({
    items_per_page: 10,
    num_display_entries: 10,
    current_page: 0,
    num_edge_entries: 0,
    link_to: "javascript:;",
    prev_text: "Prev",
    next_text: "Next",
    ellipse_text: "...",
    pageId:0,
    prev_show_always: true,
    next_show_always: true,
    callback: function () {
      return false;
    }
  }, opts || {});

  return this.each(function () {
    /**
     * 计算最大分页显示数目
     */
    function numPages() {
      return Math.ceil(maxentries / opts.items_per_page);
    }
    this.init = function (){
      console.log('init')
    }
    /**
     * 极端分页的起始和结束点，这取决于current_page 和 num_display_entries.
     * @返回 {数组(Array)}
     */
    function getInterval() {
      var ne_half = Math.ceil(opts.num_display_entries / 2);
      var np = numPages();
      var upper_limit = np - opts.num_display_entries;
      var start = current_page > ne_half ? Math.max(Math.min(current_page - ne_half, upper_limit), 0) : 0;
      var end = current_page > ne_half ? Math.min(current_page + ne_half, np) : Math.min(opts.num_display_entries, np);
      return [start, end];
    }

    /**
     * 分页链接事件处理函数
     * @参数 {int} page_id 为新页码
     */
    function pageSelected(page_id, evt) {
      current_page = page_id;
      drawLinks();
      var continuePropagation = opts.callback(page_id, panel);
      if (!continuePropagation) {
        if (evt.stopPropagation) {
          evt.stopPropagation();
        }
        else {
          evt.cancelBubble = true;
        }
      }
      return continuePropagation;
    }

    /**
     * 此函数将分页链接插入到容器元素中
     */
    function drawLinks() {
      panel.empty();
      var interval = getInterval();
      var np = numPages();
      // 这个辅助函数返回一个处理函数调用有着正确page_id的pageSelected。
      var getClickHandler = function (page_id) {
        return function (evt) {
          return pageSelected(page_id, evt);
        }
      }
      //辅助函数用来产生一个单链接(如果不是当前页则产生span标签)
      var appendItem = function (page_id, appendopts) {
        page_id = page_id < 0 ? 0 : (page_id < np ? page_id : np - 1); // 规范page id值
        this.pageId = page_id+ 1;
        appendopts = jQuery.extend({text:page_id+ 1, classes: ""}, appendopts || {});
        if (page_id == current_page) {
          var lnk = jQuery("<span class='current'>" + (appendopts.text) + "</span>");
        } else {
          var lnk = jQuery("<a>" + (appendopts.text) + "</a>")
            .bind("click", getClickHandler(page_id))
            .attr('href', opts.link_to.replace(/__id__/, page_id));
        }
        if (appendopts.classes) {
          lnk.addClass(appendopts.classes);
        }
        panel.append(lnk);
      }
      // 产生"Previous"-链接
      if (opts.prev_text && (current_page > 0 || opts.prev_show_always)) {
        appendItem(0,{text:"首页",classes:"index"});
        appendItem(current_page - 1, {text: opts.prev_text, classes: "prev"});
      }
      // 产生起始点
      if (interval[0] > 0 && opts.num_edge_entries > 0) {
        var end = Math.min(opts.num_edge_entries, interval[0]);
        for (var i = 0; i < end; i++) {
          appendItem(i);
        }
        if (opts.num_edge_entries < interval[0] && opts.ellipse_text) {
          jQuery("<span>" + opts.ellipse_text + "</span>").appendTo(panel);
        }
      }
      // 产生内部的些链接
      for (var i = interval[0]; i < interval[1]; i++) {
        appendItem(i);
      }
      // 产生结束点
      if (interval[1] < np && opts.num_edge_entries > 0) {
        if (np - opts.num_edge_entries > interval[1] && opts.ellipse_text) {
          jQuery("<span>" + opts.ellipse_text + "</span>").appendTo(panel);
        }
        var begin = Math.max(np - opts.num_edge_entries, interval[1]);
        for (var i = begin; i < np; i++) {
          appendItem(i);
        }

      }
      // 产生 "Next"-链接
      if (opts.next_text && (current_page < np - 1 || opts.next_show_always)) {
        appendItem(current_page + 1, {text: opts.next_text, classes: "next"});
        appendItem(maxentries,{text:"末页",classes:"last"})
      }
    }

    //从选项中提取current_page
    var current_page = opts.current_page;
    //创建一个显示条数和每页显示条数值
    maxentries = (!maxentries || maxentries < 0) ? 1 : maxentries;
    opts.items_per_page = (!opts.items_per_page || opts.items_per_page < 0) ? 1 : opts.items_per_page;
    //存储DOM元素，以方便从所有的内部结构中获取
    var panel = jQuery(this);
    // 获得附加功能的元素
    this.selectPage = function (page_id) {
      pageSelected(page_id);
    }
    this.prevPage = function () {
      if (current_page > 0) {
        pageSelected(current_page - 1);
        return true;
      }
      else {
        return false;
      }
    }
    this.nextPage = function () {
      if (current_page < numPages() - 1) {
        pageSelected(current_page + 1);
        return true;
      }
      else {
        return false;
      }
    }
    // 所有初始化完成，绘制链接
    drawLinks();
    // 回调函数
    //opts.callback(current_page, this);
  });
}